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ZFS(8) FreeBSD System Manager's Manual ZFS(8)
NAMEzfs -- configures ZFS file systems
SYNOPSISzfs [-?]
zfscreate [-pu] [-oproperty=value]... filesystemzfscreate [-ps] [-bblocksize] [-oproperty=value]... -Vsizevolumezfsdestroy [-fnpRrv] filesystem|volumezfsdestroy [-dnpRrv] filesystem|volume@snap[%snap][,snap[%snap]][,...]
zfsdestroyfilesystem|volume#bookmarkzfssnapshot|snap [-r] [-oproperty=value]...
filesystem@snapname|volume@snapnamefilesystem@snapname|volume@snapname...
zfsrollback [-rRf] snapshotzfsclone [-p] [-oproperty=value]... snapshotfilesystem|volumezfspromoteclone-filesystemzfsrename [-f] filesystem|volume|snapshotfilesystem|volume|snapshotzfsrename [-f] -pfilesystem|volumefilesystem|volumezfsrename-rsnapshotsnapshotzfsrename-u [-p] filesystemfilesystemzfslist [-r|-ddepth] [-Hp] [-oproperty[,property]...]
[-ttype[,type]...] [-sproperty]... [-Sproperty]...
filesystem|volume|snapshotzfssetproperty=valuefilesystem|volume|snapshot...
zfsget [-r|-ddepth] [-Hp] [-oall | field[,field]...]
[-ttype[, type]...] [-ssource[,source]...] all |
property[,property]... filesystem|volume|snapshot...
zfsinherit [-rS] propertyfilesystem|volume|snapshot...
zfsupgrade [-v]
zfsupgrade [-r] [-Vversion] -a | filesystemzfsuserspace [-Hinp] [-ofield[,field]...] [-sfield]... [-Sfield]...
[-ttype[,type]...] filesystem|snapshotzfsgroupspace [-Hinp] [-ofield[,field]...] [-sfield]... [-Sfield]...
[-ttype[,type]...] filesystem|snapshotzfsmountzfsmount [-vO] [-oproperty[,property]...] -a | filesystemzfsunmount|umount [-f] -a | filesystem|mountpointzfsshare-a | filesystemzfsunshare-a | filesystem|mountpointzfsbookmarksnapshotbookmarkzfssend [-DnPpRve] [-isnapshot | -Isnapshot] snapshotzfssend [-e] [-isnapshot|bookmark] filesystem|volume|snapshotzfsreceive|recv [-vnFu] filesystem|volume|snapshotzfsreceive|recv [-vnFu] [-d | -e] filesystemzfsallowfilesystem|volumezfsallow [-ldug] user|group[,user|group]...
perm|@setname[,perm|@setname]... filesystem|volumezfsallow [-ld] -e|everyoneperm|@setname[,perm|@setname]...
filesystem|volumezfsallow-cperm|@setname[,perm|@setname]... filesystem|volumezfsallow-s@setnameperm|@setname[,perm|@setname]... filesystem|volumezfsunallow [-rldug] user|group[,user|group]...
[perm|@setname[,perm|@setname]...] filesystem|volumezfsunallow [-rld] -e|everyone [perm|@setname[,perm|@setname]...]
filesystem|volumezfsunallow [-r] -c [perm|@setname[,perm|@setname]...] filesystem|volumezfsunallow [-r] -s@setname [perm|@setname[,perm|@setname]...]
filesystem|volumezfshold [-r] tagsnapshot...
zfsholds [-r] snapshot...
zfsrelease [-r] tagsnapshot...
zfsdiff [-FHt] snapshot [snapshot|filesystem]
zfsjailjailid|jailnamefilesystemzfsunjailjailid|jailnamefilesystemDESCRIPTION
The zfs command configures ZFS datasets within a ZFS storage pool, as
described in zpool(8). A dataset is identified by a unique path within
the ZFS namespace. For example:
pool/{filesystem,volume,snapshot}
where the maximum length of a dataset name is MAXNAMELEN (256 bytes).
A dataset can be one of the following:
filesystem A ZFS dataset of type filesystem can be mounted within the
standard system namespace and behaves like other file sys-
tems. While ZFS file systems are designed to be POSIX com-
pliant, known issues exist that prevent compliance in some
cases. Applications that depend on standards conformance
might fail due to nonstandard behavior when checking file
system free space.
volume A logical volume exported as a raw or block device. This
type of dataset should only be used under special circum-
stances. File systems are typically used in most environ-
ments.
snapshot A read-only version of a file system or volume at a given
point in time. It is specified as filesystem@name or
volume@name.
ZFSFileSystemHierarchy
A ZFS storage pool is a logical collection of devices that provide space
for datasets. A storage pool is also the root of the ZFS file system
hierarchy.
The root of the pool can be accessed as a file system, such as mounting
and unmounting, taking snapshots, and setting properties. The physical
storage characteristics, however, are managed by the zpool(8) command.
See zpool(8) for more information on creating and administering pools.
Snapshots
A snapshot is a read-only copy of a file system or volume. Snapshots can
be created extremely quickly, and initially consume no additional space
within the pool. As data within the active dataset changes, the snapshot
consumes more data than would otherwise be shared with the active
dataset.
Snapshots can have arbitrary names. Snapshots of volumes can be cloned or
rolled back, but cannot be accessed independently.
File system snapshots can be accessed under the .zfs/snapshot directory
in the root of the file system. Snapshots are automatically mounted on
demand and may be unmounted at regular intervals. The visibility of the
.zfs directory can be controlled by the snapdir property.
Clones
A clone is a writable volume or file system whose initial contents are
the same as another dataset. As with snapshots, creating a clone is
nearly instantaneous, and initially consumes no additional space.
Clones can only be created from a snapshot. When a snapshot is cloned, it
creates an implicit dependency between the parent and child. Even though
the clone is created somewhere else in the dataset hierarchy, the origi-
nal snapshot cannot be destroyed as long as a clone exists. The origin
property exposes this dependency, and the destroy command lists any such
dependencies, if they exist.
The clone parent-child dependency relationship can be reversed by using
the promote subcommand. This causes the "origin" file system to become a
clone of the specified file system, which makes it possible to destroy
the file system that the clone was created from.
MountPoints
Creating a ZFS file system is a simple operation, so the number of file
systems per system is likely to be numerous. To cope with this, ZFS auto-
matically manages mounting and unmounting file systems without the need
to edit the /etc/fstab file. All automatically managed file systems are
mounted by ZFS at boot time.
By default, file systems are mounted under /path, where path is the name
of the file system in the ZFS namespace. Directories are created and
destroyed as needed.
A file system can also have a mount point set in the mountpoint property.
This directory is created as needed, and ZFS automatically mounts the
file system when the "zfsmount-a" command is invoked (without editing
/etc/fstab). The mountpoint property can be inherited, so if pool/home
has a mount point of /home, then pool/home/user automatically inherits a
mount point of /home/user.
A file system mountpoint property of none prevents the file system from
being mounted.
If needed, ZFS file systems can also be managed with traditional tools
(mount(8), umount(8), fstab(5)). If a file system's mount point is set
to legacy, ZFS makes no attempt to manage the file system, and the admin-
istrator is responsible for mounting and unmounting the file system.
Jails
A ZFS dataset can be attached to a jail by using the "zfsjail" subcom-
mand. You cannot attach a dataset to one jail and the children of the
same dataset to another jails. To allow management of the dataset from
within a jail, the jailed property has to be set and the jail needs
access to the /dev/zfs device. The quota property cannot be changed from
within a jail. See jail(8) for information on how to allow mounting ZFS
datasets from within a jail.
A ZFS dataset can be detached from a jail using the "zfsunjail" subcom-
mand.
After a dataset is attached to a jail and the jailed property is set, a
jailed file system cannot be mounted outside the jail, since the jail
administrator might have set the mount point to an unacceptable value.
Deduplication
Deduplication is the process for removing redundant data at the block-
level, reducing the total amount of data stored. If a file system has the
dedup property enabled, duplicate data blocks are removed synchronously.
The result is that only unique data is stored and common components are
shared among files.
NativeProperties
Properties are divided into two types, native properties and user-defined
(or "user") properties. Native properties either export internal statis-
tics or control ZFS behavior. In addition, native properties are either
editable or read-only. User properties have no effect on ZFS behavior,
but you can use them to annotate datasets in a way that is meaningful in
your environment. For more information about user properties, see the
"UserProperties" section, below.
Every dataset has a set of properties that export statistics about the
dataset as well as control various behaviors. Properties are inherited
from the parent unless overridden by the child. Some properties apply
only to certain types of datasets (file systems, volumes, or snapshots).
The values of numeric properties can be specified using human-readable
suffixes (for example, k, KB, M, Gb, and so forth, up to Z for
zettabyte). The following are all valid (and equal) specifications:
1536M, 1.5g, 1.50GB
The values of non-numeric properties are case sensitive and must be low-
ercase, except for mountpoint, sharenfs, and sharesmb.
The following native properties consist of read-only statistics about the
dataset. These properties can be neither set, nor inherited. Native prop-
erties apply to all dataset types unless otherwise noted.
available
The amount of space available to the dataset and all its children,
assuming that there is no other activity in the pool. Because space
is shared within a pool, availability can be limited by any number of
factors, including physical pool size, quotas, reservations, or other
datasets within the pool.
This property can also be referred to by its shortened column name,
avail.
compressratio
For non-snapshots, the compression ratio achieved for the used space
of this dataset, expressed as a multiplier. The used property
includes descendant datasets, and, for clones, does not include the
space shared with the origin snapshot. For snapshots, the
compressratio is the same as the refcompressratio property. Compres-
sion can be turned on by running: "zfssetcompression=ondataset"
The default value is off.
creation
The time this dataset was created.
clones
For snapshots, this property is a comma-separated list of filesystems
or volumes which are clones of this snapshot. The clones' origin
property is this snapshot. If the clones property is not empty, then
this snapshot can not be destroyed (even with the -r or -f options).
defer_destroy
This property is on if the snapshot has been marked for deferred
destroy by using the "zfsdestroy-d" command. Otherwise, the prop-
erty is off.
filesystem_count
The total number of filesystems and volumes that exist under this
location in the dataset tree. This value is only available when a
filesystem_limit has been set somewhere in the tree under which the
dataset resides.
logicalreferenced
The amount of space that is "logically" accessible by this dataset.
See the referenced property. The logical space ignores the effect of
the compression and copies properties, giving a quantity closer to
the amount of data that applications see. However, it does include
space consumed by metadata.
This property can also be referred to by its shortened column name,
lrefer.
logicalused
The amount of space that is "logically" consumed by this dataset and
all its descendents. See the used property. The logical space
ignores the effect of the compression and copies properties, giving a
quantity closer to the amount of data that applications see.
This property can also be referred to by its shortened column name,
lused.
mounted
For file systems, indicates whether the file system is currently
mounted. This property can be either yes or no.
origin
For cloned file systems or volumes, the snapshot from which the clone
was created. See also the clones property.
referenced
The amount of data that is accessible by this dataset, which may or
may not be shared with other datasets in the pool. When a snapshot or
clone is created, it initially references the same amount of space as
the file system or snapshot it was created from, since its contents
are identical.
This property can also be referred to by its shortened column name,
refer.
refcompressratio
The compression ratio achieved for the referenced space of this
dataset, expressed as a multiplier. See also the compressratio prop-
erty.
snapshot_count
The total number of snapshots that exist under this location in the
dataset tree. This value is only available when a snapshot_limit has
been set somewhere in the tree under which the dataset resides.
type
The type of dataset: filesystem, volume, or snapshot.
used
The amount of space consumed by this dataset and all its descendents.
This is the value that is checked against this dataset's quota and
reservation. The space used does not include this dataset's reserva-
tion, but does take into account the reservations of any descendent
datasets. The amount of space that a dataset consumes from its par-
ent, as well as the amount of space that are freed if this dataset is
recursively destroyed, is the greater of its space used and its
reservation.
When snapshots (see the "Snapshots" section) are created, their space
is initially shared between the snapshot and the file system, and
possibly with previous snapshots. As the file system changes, space
that was previously shared becomes unique to the snapshot, and
counted in the snapshot's space used. Additionally, deleting snap-
shots can increase the amount of space unique to (and used by) other
snapshots.
The amount of space used, available, or referenced does not take into
account pending changes. Pending changes are generally accounted for
within a few seconds. Committing a change to a disk using fsync(2) or
O_SYNC does not necessarily guarantee that the space usage informa-
tion is updated immediately.
usedby*
The usedby* properties decompose the used properties into the various
reasons that space is used. Specifically, used = usedbysnapshots+usedbydataset+usedbychildren+usedbyrefreservation. These proper-
ties are only available for datasets created with ZFS pool version 13
pools and higher.
usedbysnapshots
The amount of space consumed by snapshots of this dataset. In partic-
ular, it is the amount of space that would be freed if all of this
dataset's snapshots were destroyed. Note that this is not simply the
sum of the snapshots' used properties because space can be shared by
multiple snapshots.
usedbydataset
The amount of space used by this dataset itself, which would be freed
if the dataset were destroyed (after first removing any
refreservation and destroying any necessary snapshots or descen-
dents).
usedbychildren
The amount of space used by children of this dataset, which would be
freed if all the dataset's children were destroyed.
usedbyrefreservation
The amount of space used by a refreservation set on this dataset,
which would be freed if the refreservation was removed.
userused@user
The amount of space consumed by the specified user in this dataset.
Space is charged to the owner of each file, as displayed by "ls-l".
The amount of space charged is displayed by "du" and "ls-s". See
the "zfsuserspace" subcommand for more information.
Unprivileged users can access only their own space usage. The root
user, or a user who has been granted the userused privilege with "zfsallow", can access everyone's usage.
The userused@... properties are not displayed by "zfsgetall". The
user's name must be appended after the @ symbol, using one of the
following forms:
+o POSIX name (for example, joe)
+o POSIX numeric ID (for example, 1001)
userrefs
This property is set to the number of user holds on this snapshot.
User holds are set by using the "zfshold" command.
groupused@group
The amount of space consumed by the specified group in this dataset.
Space is charged to the group of each file, as displayed by ls-l.
See the userused@user property for more information.
Unprivileged users can only access their own groups' space usage. The
root user, or a user who has been granted the groupused privilege
with "zfsallow", can access all groups' usage.
volblocksize=blocksize
For volumes, specifies the block size of the volume. The blocksize
cannot be changed once the volume has been written, so it should be
set at volume creation time. The default blocksize for volumes is 8
Kbytes. Any power of 2 from 512 bytes to 128 Kbytes is valid.
This property can also be referred to by its shortened column name,
volblock.
written
The amount of referenced space written to this dataset since the pre-
vious snapshot.
written@snapshot
The amount of referenced space written to this dataset since the
specified snapshot. This is the space that is referenced by this
dataset but was not referenced by the specified snapshot.
The snapshot may be specified as a short snapshot name (just the part
after the @), in which case it will be interpreted as a snapshot in
the same filesystem as this dataset. The snapshot may be a full snap-
shot name (filesystem@snapshot), which for clones may be a snapshot
in the origin's filesystem (or the origin of the origin's filesystem,
etc).
The following native properties can be used to change the behavior of a
ZFS dataset.
aclinherit=discard | noallow | restricted | passthrough | passthrough-x
Controls how ACL entries are inherited when files and directories are
created. A file system with an aclinherit property of discard does
not inherit any ACL entries. A file system with an aclinherit prop-
erty value of noallow only inherits inheritable ACL entries that
specify "deny" permissions. The property value restricted (the
default) removes the write_acl and write_owner permissions when the
ACL entry is inherited. A file system with an aclinherit property
value of passthrough inherits all inheritable ACL entries without any
modifications made to the ACL entries when they are inherited. A file
system with an aclinherit property value of passthrough-x has the
same meaning as passthrough, except that the owner@, group@, and
everyone@ ACEs inherit the execute permission only if the file cre-
ation mode also requests the execute bit.
When the property value is set to passthrough, files are created with
a mode determined by the inheritable ACEs. If no inheritable ACEs
exist that affect the mode, then the mode is set in accordance to the
requested mode from the application.
aclmode=discard | groupmask | passthrough | restricted
Controls how an ACL is modified during chmod(2). A file system with
an aclmode property of discard (the default) deletes all ACL entries
that do not represent the mode of the file. An aclmode property of
groupmask reduces permissions granted in all ALLOW entries found in
the ACL such that they are no greater than the group permissions
specified by chmod(2). A file system with an aclmode property of
passthrough indicates that no changes are made to the ACL other than
creating or updating the necessary ACL entries to represent the new
mode of the file or directory. An aclmode property of restricted
will cause the chmod(2) operation to return an error when used on any
file or directory which has a non-trivial ACL whose entries can not
be represented by a mode. chmod(2) is required to change the set
user ID, set group ID, or sticky bits on a file or directory, as they
do not have equivalent ACL entries. In order to use chmod(2) on a
file or directory with a non-trivial ACL when aclmode is set to
restricted, you must first remove all ACL entries which do not repre-
sent the current mode.
atime=on | off
Controls whether the access time for files is updated when they are
read. Turning this property off avoids producing write traffic when
reading files and can result in significant performance gains, though
it might confuse mailers and other similar utilities. The default
value is on.
canmount=on | off | noauto
If this property is set to off, the file system cannot be mounted,
and is ignored by "zfsmount-a". Setting this property to off is
similar to setting the mountpoint property to none, except that the
dataset still has a normal mountpoint property, which can be inher-
ited. Setting this property to off allows datasets to be used solely
as a mechanism to inherit properties. One example of setting
canmount=off is to have two datasets with the same mountpoint, so
that the children of both datasets appear in the same directory, but
might have different inherited characteristics.
When the noauto value is set, a dataset can only be mounted and
unmounted explicitly. The dataset is not mounted automatically when
the dataset is created or imported, nor is it mounted by the "zfsmount-a" command or unmounted by the "zfsumount-a" command.
This property is not inherited.
checksum=on | off | fletcher2 | fletcher4 | sha256 | noparity
Controls the checksum used to verify data integrity. The default
value is on, which automatically selects an appropriate algorithm
(currently, fletcher4, but this may change in future releases). The
value off disables integrity checking on user data. The value
noparity not only disables integrity but also disables maintaining
parity for user data. This setting is used internally by a dump
device residing on a RAID-Z pool and should not be used by any other
dataset. Disabling checksums is NOT a recommended practice.
compression=on | off | lzjb | gzip | gzip-N | zle | lz4
Controls the compression algorithm used for this dataset. The lzjb
compression algorithm is optimized for performance while providing
decent data compression. Setting compression to on uses the lzjb com-
pression algorithm. The gzip compression algorithm uses the same com-
pression as the gzip(1) command. You can specify the gzip level by
using the value gzip-N where N is an integer from 1 (fastest) to 9
(best compression ratio). Currently, gzip is equivalent to gzip-6
(which is also the default for gzip(1)). The zle compression algo-
rithm compresses runs of zeros.
The lz4 compression algorithm is a high-performance replacement for
the lzjb algorithm. It features significantly faster compression and
decompression, as well as a moderately higher compression ratio than
lzjb, but can only be used on pools with the lz4_compress feature set
to enabled. See zpool-features(7) for details on ZFS feature flags
and the lz4_compress feature.
This property can also be referred to by its shortened column name
compress. Changing this property affects only newly-written data.
copies=1 | 2 | 3
Controls the number of copies of data stored for this dataset. These
copies are in addition to any redundancy provided by the pool, for
example, mirroring or RAID-Z. The copies are stored on different
disks, if possible. The space used by multiple copies is charged to
the associated file and dataset, changing the used property and
counting against quotas and reservations.
Changing this property only affects newly-written data. Therefore,
set this property at file system creation time by using the -ocopies=N option.
dedup=on | off | verify | sha256[,verify]
Configures deduplication for a dataset. The default value is off.
The default deduplication checksum is sha256 (this may change in the
future). When dedup is enabled, the checksum defined here overrides
the checksum property. Setting the value to verify has the same
effect as the setting sha256,verify.
If set to verify, ZFS will do a byte-to-byte comparsion in case of
two blocks having the same signature to make sure the block contents
are identical.
devices=on | off
The devices property is currently not supported on FreeBSD.
exec=on | off
Controls whether processes can be executed from within this file sys-
tem. The default value is on.
mlslabel=label | none
The mlslabel property is currently not supported on FreeBSD.
filesystem_limit=count | none
Limits the number of filesystems and volumes that can exist under
this point in the dataset tree. The limit is not enforced if the
user is allowed to change the limit. Setting a filesystem_limit on a
descendent of a filesystem that already has a filesystem_limit does
not override the ancestor's filesystem_limit, but rather imposes an
additional limit. This feature must be enabled to be used (see
zpool-features(7)).
mountpoint=path | none | legacy
Controls the mount point used for this file system. See the "MountPoints" section for more information on how this property is used.
When the mountpoint property is changed for a file system, the file
system and any children that inherit the mount point are unmounted.
If the new value is legacy, then they remain unmounted. Otherwise,
they are automatically remounted in the new location if the property
was previously legacy or none, or if they were mounted before the
property was changed. In addition, any shared file systems are
unshared and shared in the new location.
nbmand=on | off
The nbmand property is currently not supported on FreeBSD.
primarycache=all | none | metadata
Controls what is cached in the primary cache (ARC). If this property
is set to all, then both user data and metadata is cached. If this
property is set to none, then neither user data nor metadata is
cached. If this property is set to metadata, then only metadata is
cached. The default value is all.
quota=size | none
Limits the amount of space a dataset and its descendents can consume.
This property enforces a hard limit on the amount of space used. This
includes all space consumed by descendents, including file systems
and snapshots. Setting a quota on a descendent of a dataset that
already has a quota does not override the ancestor's quota, but
rather imposes an additional limit.
Quotas cannot be set on volumes, as the volsize property acts as an
implicit quota.
snapshot_limit=count | none
Limits the number of snapshots that can be created on a dataset and
its descendents. Setting a snapshot_limit on a descendent of a
dataset that already has a snapshot_limit does not override the
ancestor's snapshot_limit, but rather imposes an additional limit.
The limit is not enforced if the user is allowed to change the limit.
For example, this means that recursive snapshots taken from the
global zone are counted against each delegated dataset within a jail.
This feature must be enabled to be used (see zpool-features(7)).
userquota@user=size | none
Limits the amount of space consumed by the specified user. Similar
to the refquota property, the userquota space calculation does not
include space that is used by descendent datasets, such as snapshots
and clones. User space consumption is identified by the
userspace@user property.
Enforcement of user quotas may be delayed by several seconds. This
delay means that a user might exceed their quota before the system
notices that they are over quota and begins to refuse additional
writes with the EDQUOT error message. See the userspace subcommand
for more information.
Unprivileged users can only access their own groups' space usage. The
root user, or a user who has been granted the userquota privilege
with "zfsallow", can get and set everyone's quota.
This property is not available on volumes, on file systems before
version 4, or on pools before version 15. The userquota@... proper-
ties are not displayed by "zfsgetall". The user's name must be
appended after the @ symbol, using one of the following forms:
+o POSIX name (for example, joe)
+o POSIX numeric ID (for example, 1001)
groupquota@group=size | none
Limits the amount of space consumed by the specified group. Group
space consumption is identified by the userquota@user property.
Unprivileged users can access only their own groups' space usage. The
root user, or a user who has been granted the groupquota privilege
with "zfsallow", can get and set all groups' quotas.
readonly=on | off
Controls whether this dataset can be modified. The default value is
off.
recordsize=size
Specifies a suggested block size for files in the file system. This
property is designed solely for use with database workloads that
access files in fixed-size records. ZFS automatically tunes block
sizes according to internal algorithms optimized for typical access
patterns.
For databases that create very large files but access them in small
random chunks, these algorithms may be suboptimal. Specifying a
recordsize greater than or equal to the record size of the database
can result in significant performance gains. Use of this property for
general purpose file systems is strongly discouraged, and may
adversely affect performance.
The size specified must be a power of two greater than or equal to
512 and less than or equal to 128 Kbytes.
Changing the file system's recordsize affects only files created
afterward; existing files are unaffected.
This property can also be referred to by its shortened column name,
recsize.
redundant_metadata=all | most
Controls what types of metadata are stored redundantly. ZFS stores
an extra copy of metadata, so that if a single block is corrupted,
the amount of user data lost is limited. This extra copy is in addi-
tion to any redundancy provided at the pool level (e.g. by mirroring
or RAID-Z), and is in addition to an extra copy specified by the
copies property (up to a total of 3 copies). For example if the pool
is mirrored, copies=2, and redundant_metadata=most, then ZFS stores 6
copies of most metadata, and 4 copies of data and some metadata.
When set to all, ZFS stores an extra copy of all metadata. If a sin-
gle on-disk block is corrupt, at worst a single block of user data
(which is recordsize bytes long can be lost.)
When set to most, ZFS stores an extra copy of most types of metadata.
This can improve performance of random writes, because less metadata
must be written. In practice, at worst about 100 blocks (of
recordsize bytes each) of user data can be lost if a single on-disk
block is corrupt. The exact behavior of which metadata blocks are
stored redundantly may change in future releases.
The default value is all.
refquota=size | none
Limits the amount of space a dataset can consume. This property
enforces a hard limit on the amount of space used. This hard limit
does not include space used by descendents, including file systems
and snapshots.
refreservation=size | none
The minimum amount of space guaranteed to a dataset, not including
its descendents. When the amount of space used is below this value,
the dataset is treated as if it were taking up the amount of space
specified by refreservation. The refreservation reservation is
accounted for in the parent datasets' space used, and counts against
the parent datasets' quotas and reservations.
If refreservation is set, a snapshot is only allowed if there is
enough free pool space outside of this reservation to accommodate the
current number of "referenced" bytes in the dataset.
This property can also be referred to by its shortened column name,
refreserv.
reservation=size | none
The minimum amount of space guaranteed to a dataset and its descen-
dents. When the amount of space used is below this value, the dataset
is treated as if it were taking up the amount of space specified by
its reservation. Reservations are accounted for in the parent
datasets' space used, and count against the parent datasets' quotas
and reservations.
This property can also be referred to by its shortened column name,
reserv.
secondarycache=all | none | metadata
Controls what is cached in the secondary cache (L2ARC). If this prop-
erty is set to all, then both user data and metadata is cached. If
this property is set to none, then neither user data nor metadata is
cached. If this property is set to metadata, then only metadata is
cached. The default value is all.
setuid=on | off
Controls whether the set-UID bit is respected for the file system.
The default value is on.
sharesmb=on | off | opts
The sharesmb property currently has no effect on FreeBSD.
sharenfs=on | off | opts
Controls whether the file system is shared via NFS, and what options
are used. A file system with a sharenfs property of off is managed
the traditional way via exports(5). Otherwise, the file system is
automatically shared and unshared with the "zfsshare" and "zfsunshare" commands. If the property is set to on no NFS export options
are used. Otherwise, NFS export options are equivalent to the con-
tents of this property. The export options may be comma-separated.
See exports(5) for a list of valid options.
When the sharenfs property is changed for a dataset, the mountd(8)
daemon is reloaded.
logbias=latency | throughput
Provide a hint to ZFS about handling of synchronous requests in this
dataset. If logbias is set to latency (the default), ZFS will use
pool log devices (if configured) to handle the requests at low
latency. If logbias is set to throughput, ZFS will not use configured
pool log devices. ZFS will instead optimize synchronous operations
for global pool throughput and efficient use of resources.
snapdir=hidden | visible
Controls whether the .zfs directory is hidden or visible in the root
of the file system as discussed in the "Snapshots" section. The
default value is hidden.
sync=standard | always | disabled
Controls the behavior of synchronous requests (e.g. fsync(2),
O_DSYNC). This property accepts the following values:
standard This is the POSIX specified behavior of ensuring all
synchronous requests are written to stable storage and
all devices are flushed to ensure data is not cached by
device controllers (this is the default).
always All file system transactions are written and flushed
before their system calls return. This has a large per-
formance penalty.
disabled Disables synchronous requests. File system transactions
are only committed to stable storage periodically. This
option will give the highest performance. However, it
is very dangerous as ZFS would be ignoring the synchro-
nous transaction demands of applications such as data-
bases or NFS. Administrators should only use this
option when the risks are understood.
volsize=size
For volumes, specifies the logical size of the volume. By default,
creating a volume establishes a reservation of equal size. For stor-
age pools with a version number of 9 or higher, a refreservation is
set instead. Any changes to volsize are reflected in an equivalent
change to the reservation (or refreservation). The volsize can only
be set to a multiple of volblocksize, and cannot be zero.
The reservation is kept equal to the volume's logical size to prevent
unexpected behavior for consumers. Without the reservation, the vol-
ume could run out of space, resulting in undefined behavior or data
corruption, depending on how the volume is used. These effects can
also occur when the volume size is changed while it is in use (par-
ticularly when shrinking the size). Extreme care should be used when
adjusting the volume size.
Though not recommended, a "sparse volume" (also known as "thin provi-
sioning") can be created by specifying the -s option to the "zfscreate-V" command, or by changing the reservation after the volume
has been created. A "sparse volume" is a volume where the reservation
is less then the volume size. Consequently, writes to a sparse vol-
ume can fail with ENOSPC when the pool is low on space. For a sparse
volume, changes to volsize are not reflected in the reservation.
volmode=default | geom | dev | none
This property specifies how volumes should be exposed to the OS.
Setting it to geom exposes volumes as geom(4) providers, providing
maximal functionality. Setting it to dev exposes volumes only as
cdev device in devfs. Such volumes can be accessed only as raw disk
device files, i.e. they can not be partitioned, mounted, participate
in RAIDs, etc, but they are faster, and in some use scenarios with
untrusted consumer, such as NAS or VM storage, can be more safe.
Volumes with property set to none are not exposed outside ZFS, but
can be snapshoted, cloned, replicated, etc, that can be suitable for
backup purposes. Value default means that volumes exposition is con-
trolled by system-wide sysctl/tunable vfs.zfs.vol.mode, where geom,
dev and none are encoded as 1, 2 and 3 respectively. The default
values is geom. This property can be changed any time, but so far it
is processed only during volume creation and pool import.
vscan=off | on
The vscan property is currently not supported on FreeBSD.
xattr=off | on
The xattr property is currently not supported on FreeBSD.
jailed=off | on
Controls whether the dataset is managed from a jail. See the "Jails"
section for more information. The default value is off.
The following three properties cannot be changed after the file system is
created, and therefore, should be set when the file system is created. If
the properties are not set with the "zfscreate" or zpoolcreate com-
mands, these properties are inherited from the parent dataset. If the
parent dataset lacks these properties due to having been created prior to
these features being supported, the new file system will have the default
values for these properties.
casesensitivity=sensitive | insensitive | mixed
Indicates whether the file name matching algorithm used by the file
system should be case-sensitive, case-insensitive, or allow a com-
bination of both styles of matching. The default value for the
casesensitivity property is sensitive. Traditionally, UNIX and
POSIX file systems have case-sensitive file names.
The mixed value for the casesensitivity property indicates that the
file system can support requests for both case-sensitive and case-
insensitive matching behavior.
normalization=none | formC | formD | formKC | formKD
Indicates whether the file system should perform a unicode normal-
ization of file names whenever two file names are compared, and
which normalization algorithm should be used. File names are always
stored unmodified, names are normalized as part of any comparison
process. If this property is set to a legal value other than none,
and the utf8only property was left unspecified, the utf8only prop-
erty is automatically set to on. The default value of the
normalization property is none. This property cannot be changed
after the file system is created.
utf8only=on | off
Indicates whether the file system should reject file names that
include characters that are not present in the UTF-8 character code
set. If this property is explicitly set to off, the normalization
property must either not be explicitly set or be set to none. The
default value for the utf8only property is off. This property can-
not be changed after the file system is created.
The casesensitivity, normalization, and utf8only properties are also new
permissions that can be assigned to non-privileged users by using the ZFS
delegated administration feature.
TemporaryMountPointProperties
When a file system is mounted, either through mount(8) for legacy mounts
or the "zfsmount" command for normal file systems, its mount options are
set according to its properties. The correlation between properties and
mount options is as follows:
PROPERTY MOUNT OPTION
atime atime/noatime
exec exec/noexec
readonly ro/rw
setuid suid/nosuid
In addition, these options can be set on a per-mount basis using the -o
option, without affecting the property that is stored on disk. The values
specified on the command line override the values stored in the dataset.
These properties are reported as "temporary" by the "zfsget" command. If
the properties are changed while the dataset is mounted, the new setting
overrides any temporary settings.
UserProperties
In addition to the standard native properties, ZFS supports arbitrary
user properties. User properties have no effect on ZFS behavior, but
applications or administrators can use them to annotate datasets (file
systems, volumes, and snapshots).
User property names must contain a colon (:) character to distinguish
them from native properties. They may contain lowercase letters, numbers,
and the following punctuation characters: colon (:), dash (-), period (.)
and underscore (_). The expected convention is that the property name is
divided into two portions such as module:property, but this namespace is
not enforced by ZFS. User property names can be at most 256 characters,
and cannot begin with a dash (-).
When making programmatic use of user properties, it is strongly suggested
to use a reversed DNS domain name for the module component of property
names to reduce the chance that two independently-developed packages use
the same property name for different purposes. Property names beginning
with com.sun are reserved for use by Sun Microsystems.
The values of user properties are arbitrary strings, are always inher-
ited, and are never validated. All of the commands that operate on prop-
erties ("zfslist", "zfsget", "zfsset" and so forth) can be used to
manipulate both native properties and user properties. Use the "zfsinherit" command to clear a user property. If the property is not defined
in any parent dataset, it is removed entirely. Property values are lim-
ited to 1024 characters.
SUBCOMMANDS
All subcommands that modify state are logged persistently to the pool in
their original form.
zfs [-?]
Displays a help message.
zfscreate [-pu] [-oproperty=value]... filesystem
Creates a new ZFS file system. The file system is automatically
mounted according to the mountpoint property inherited from the par-
ent.
-p Creates all the non-existing parent datasets. Datasets cre-
ated in this manner are automatically mounted according to
the mountpoint property inherited from their parent. Any
property specified on the command line using the -o option is
ignored. If the target filesystem already exists, the opera-
tion completes successfully.
-u Newly created file system is not mounted.
-oproperty=value
Sets the specified property as if the command "zfssetproperty=value" was invoked at the same time the dataset was
created. Any editable ZFS property can also be set at cre-
ation time. Multiple -o options can be specified. An error
results if the same property is specified in multiple -o
options.
zfscreate [-ps] [-bblocksize] [-oproperty=value]... -Vsizevolume
Creates a volume of the given size. The volume is exported as a block
device in /dev/zvol/path, where path is the name of the volume in the
ZFS namespace. The size represents the logical size as exported by
the device. By default, a reservation of equal size is created.
size is automatically rounded up to the nearest 128 Kbytes to ensure
that the volume has an integral number of blocks regardless of
blocksize.
-p Creates all the non-existing parent datasets. Datasets cre-
ated in this manner are automatically mounted according to
the mountpoint property inherited from their parent. Any
property specified on the command line using the -o option is
ignored. If the target filesystem already exists, the opera-
tion completes successfully.
-s Creates a sparse volume with no reservation. See volsize in
the "NativeProperties" section for more information about
sparse volumes.
-bblocksize
Equivalent to -ovolblocksize=blocksize. If this option is
specified in conjunction with -ovolblocksize, the resulting
behavior is undefined.
-oproperty=value
Sets the specified property as if the "zfssetproperty=value" command was invoked at the same time the
dataset was created. Any editable ZFS property can also be
set at creation time. Multiple -o options can be specified.
An error results if the same property is specified in multi-
ple -o options.
zfsdestroy [-fnpRrv] filesystem|volume
Destroys the given dataset. By default, the command unshares any file
systems that are currently shared, unmounts any file systems that are
currently mounted, and refuses to destroy a dataset that has active
dependents (children or clones).
-r Recursively destroy all children.
-R Recursively destroy all dependents, including cloned file
systems outside the target hierarchy.
-f Force an unmount of any file systems using the "zfsunmount-f" command. This option has no effect on non-file systems or
unmounted file systems.
-n Do a dry-run ("No-op") deletion. No data will be deleted.
This is useful in conjunction with the -v or -p flags to
determine what data would be deleted.
-p Print machine-parsable verbose information about the deleted
data.
-v Print verbose information about the deleted data.
Extreme care should be taken when applying either the -r or the -R
options, as they can destroy large portions of a pool and cause unex-
pected behavior for mounted file systems in use.
zfsdestroy [-dnpRrv] snapshot[%snapname][,...]
The given snapshots are destroyed immediately if and only if the "zfsdestroy" command without the -d option would have destroyed it. Such
immediate destruction would occur, for example, if the snapshot had
no clones and the user-initiated reference count were zero.
If a snapshot does not qualify for immediate destruction, it is
marked for deferred deletion. In this state, it exists as a usable,
visible snapshot until both of the preconditions listed above are
met, at which point it is destroyed.
An inclusive range of snapshots may be specified by separating the
first and last snapshots with a percent sign (%). The first and/or
last snapshots may be left blank, in which case the filesystem's old-
est or newest snapshot will be implied.
Multiple snapshots (or ranges of snapshots) of the same filesystem or
volume may be specified in a comma-separated list of snapshots. Only
the snapshot's short name (the part after the @) should be specified
when using a range or comma-separated list to identify multiple snap-
shots.
-r Destroy (or mark for deferred deletion) all snapshots with
this name in descendent file systems.
-R Recursively destroy all clones of these snapshots, including
the clones, snapshots, and children. If this flag is speci-
fied, the [fl d] flag will have no effect.
-n Do a dry-run ("No-op") deletion. No data will be deleted.
This is useful in conjunction with the -v or -p flags to
determine what data would be deleted.
-p Print machine-parsable verbose information about the deleted
data.
-v Print verbose information about the deleted data.
-d Defer snapshot deletion.
Extreme care should be taken when applying either the -r or the -R
options, as they can destroy large portions of a pool and cause unex-
pected behavior for mounted file systems in use.
zfsdestroyfilesystem|volume#bookmark
The given bookmark is destroyed.
zfssnapshot|snap [-r] [-oproperty=value]...
filesystem@snapname|volume@snapname
filesystem@snapname|volume@snapname...
Creates snapshots with the given names. All previous modifications by
successful system calls to the file system are part of the snapshots.
Snapshots are taken atomically, so that all snapshots correspond to
the same moment in time. See the "Snapshots" section for details.
-r Recursively create snapshots of all descendent datasets
-oproperty=value
Sets the specified property; see "zfscreate" for details.
zfsrollback [-rRf] snapshot
Roll back the given dataset to a previous snapshot. When a dataset is
rolled back, all data that has changed since the snapshot is dis-
carded, and the dataset reverts to the state at the time of the snap-
shot. By default, the command refuses to roll back to a snapshot
other than the most recent one. In order to do so, all intermediate
snapshots and bookmarks must be destroyed by specifying the -r
option.
The -rR options do not recursively destroy the child snapshots of a
recursive snapshot. Only direct snapshots of the specified filesys-
tem are destroyed by either of these options. To completely roll
back a recursive snapshot, you must rollback the individual child
snapshots.
-r Destroy any snapshots and bookmarks more recent than the one
specified.
-R Destroy any more recent snapshots and bookmarks, as well as
any clones of those snapshots.
-f Used with the -R option to force an unmount of any clone file
systems that are to be destroyed.
zfsclone [-p] [-oproperty=value]... snapshotfilesystem|volume
Creates a clone of the given snapshot. See the "Clones" section for
details. The target dataset can be located anywhere in the ZFS hier-
archy, and is created as the same type as the original.
-p Creates all the non-existing parent datasets. Datasets cre-
ated in this manner are automatically mounted according to
the mountpoint property inherited from their parent. If the
target filesystem or volume already exists, the operation
completes successfully.
-oproperty=value
Sets the specified property; see "zfscreate" for details.
zfspromoteclone-filesystem
Promotes a clone file system to no longer be dependent on its "ori-
gin" snapshot. This makes it possible to destroy the file system that
the clone was created from. The clone parent-child dependency rela-
tionship is reversed, so that the origin file system becomes a clone
of the specified file system.
The snapshot that was cloned, and any snapshots previous to this
snapshot, are now owned by the promoted clone. The space they use
moves from the origin file system to the promoted clone, so enough
space must be available to accommodate these snapshots. No new space
is consumed by this operation, but the space accounting is adjusted.
The promoted clone must not have any conflicting snapshot names of
its own. The rename subcommand can be used to rename any conflicting
snapshots.
zfsrename [-f] filesystem|volume|snapshotfilesystem|volume|snapshotzfsrename [-f] -pfilesystem|volumefilesystem|volumezfsrename-u [-p] filesystemfilesystem
Renames the given dataset. The new target can be located anywhere in
the ZFS hierarchy, with the exception of snapshots. Snapshots can
only be renamed within the parent file system or volume. When renam-
ing a snapshot, the parent file system of the snapshot does not need
to be specified as part of the second argument. Renamed file systems
can inherit new mount points, in which case they are unmounted and
remounted at the new mount point.
-p Creates all the nonexistent parent datasets. Datasets created
in this manner are automatically mounted according to the
mountpoint property inherited from their parent.
-u Do not remount file systems during rename. If a file system's
mountpoint property is set to legacy or none, file system is
not unmounted even if this option is not given.
-f Force unmount any filesystems that need to be unmounted in
the process. This flag has no effect if used together with
the -u flag.
zfsrename-rsnapshotsnapshot
Recursively rename the snapshots of all descendent datasets. Snap-
shots are the only dataset that can be renamed recursively.
zfslist [-r|-ddepth] [-Hp] [-oproperty[,property]...] [-ttype[,type]...] [-sproperty]... [-Sproperty]...
filesystem|volume|snapshot...
Lists the property information for the given datasets in tabular
form. If specified, you can list property information by the absolute
pathname or the relative pathname. By default, all file systems and
volumes are displayed. Snapshots are displayed if the listsnaps
property is on (the default is off). The following fields are dis-
played, name, used, available, referenced, mountpoint.
-r Recursively display any children of the dataset on the com-
mand line.
-ddepth
Recursively display any children of the dataset, limiting the
recursion to depth. A depth of 1 will display only the
dataset and its direct children.
-H Used for scripting mode. Do not print headers and separate
fields by a single tab instead of arbitrary white space.
-p Display numbers in parsable (exact) values.
-oproperty[,property]...
A comma-separated list of properties to display. The property
must be:
+o One of the properties described in the "NativeProperties" section
+o A user property
+o The value name to display the dataset name
+o The value space to display space usage properties on
file systems and volumes. This is a shortcut for speci-
fying -oname,avail,used,usedsnap,usedds,usedrefreserv,usedchild-tfilesystem,volume syntax.
-ttype[,type]...
A comma-separated list of types to display, where type is one
of filesystem, snapshot, snap, volume, bookmark, or all. For
example, specifying -tsnapshot displays only snapshots.
-sproperty
A property for sorting the output by column in ascending
order based on the value of the property. The property must
be one of the properties described in the "Properties" sec-
tion, or the special value name to sort by the dataset name.
Multiple properties can be specified at one time using multi-
ple -s property options. Multiple -s options are evaluated
from left to right in decreasing order of importance.
The following is a list of sorting criteria:
+o Numeric types sort in numeric order.
+o String types sort in alphabetical order.
+o Types inappropriate for a row sort that row to the lit-
eral bottom, regardless of the specified ordering.
+o If no sorting options are specified the existing behav-
ior of "zfslist" is preserved.
-Sproperty
Same as the -s option, but sorts by property in descending
order.
zfssetproperty=valuefilesystem|volume|snapshot
Sets the property to the given value for each dataset. Only some
properties can be edited. See the "Properties" section for more
information on what properties can be set and acceptable values.
Numeric values can be specified as exact values, or in a human-read-
able form with a suffix of B, K, M, G, T, P, E, Z (for bytes, kilo-
bytes, megabytes, gigabytes, terabytes, petabytes, exabytes, or
zettabytes, respectively). User properties can be set on snapshots.
For more information, see the "UserProperties" section.
zfsget [-r|-ddepth] [-Hp] [-oall | field[,field]...] [-ttype[,type]...] [-ssource[,source]...] all | property[,property]...
filesystem|volume|snapshot...
Displays properties for the given datasets. If no datasets are speci-
fied, then the command displays properties for all datasets on the
system. For each property, the following columns are displayed:
name Dataset name
property Property name
value Property value
source Property source. Can either be local, default, tempo-
rary, inherited, or none (-).
All columns except the RECEIVED column are displayed by default. The
columns to display can be specified by using the -o option. This com-
mand takes a comma-separated list of properties as described in the
"NativeProperties" and "UserProperties" sections.
The special value all can be used to display all properties that
apply to the given dataset's type (filesystem, volume, snapshot, or
bookmark).
-r Recursively display properties for any children.
-ddepth
Recursively display any children of the dataset, limiting the
recursion to depth. A depth of 1 will display only the
dataset and its direct children.
-H Display output in a form more easily parsed by scripts. Any
headers are omitted, and fields are explicitly separated by a
single tab instead of an arbitrary amount of space.
-p Display numbers in parsable (exact) values.
-oall | field[,field]...
A comma-separated list of columns to display. Supported val-
ues are name,property,value,received,source. Default values
are name,property,value,source. The keyword all specifies
all columns.
-ttype[,type]...
A comma-separated list of types to display, where type is one
of filesystem, snapshot, volume, or all. For example, speci-
fying -tsnapshot displays only snapshots.
-ssource[,source]...
A comma-separated list of sources to display. Those proper-
ties coming from a source other than those in this list are
ignored. Each source must be one of the following:
local,default,inherited,temporary,received,none. The default
value is all sources.
zfsinherit [-rS] propertyfilesystem|volume|snapshot...
Clears the specified property, causing it to be inherited from an
ancestor. If no ancestor has the property set, then the default value
is used. See the "Properties" section for a listing of default val-
ues, and details on which properties can be inherited.
-r Recursively inherit the given property for all children.
-S For properties with a received value, revert to this value.
This flag has no effect on properties that do not have a
received value.
zfsupgrade [-v]
Displays a list of file systems that are not the most recent version.
-v Displays ZFS filesystem versions supported by the current
software. The current ZFS filesystem version and all previous
supported versions are displayed, along with an explanation
of the features provided with each version.
zfsupgrade [-r] [-Vversion] -a | filesystem
Upgrades file systems to a new on-disk version. Once this is done,
the file systems will no longer be accessible on systems running
older versions of the software. "zfssend" streams generated from
new snapshots of these file systems cannot be accessed on systems
running older versions of the software.
In general, the file system version is independent of the pool ver-
sion. See zpool(8) for information on the zpoolupgrade command.
In some cases, the file system version and the pool version are
interrelated and the pool version must be upgraded before the file
system version can be upgraded.
-r Upgrade the specified file system and all descendent file
systems.
-Vversion
Upgrade to the specified version. If the -V flag is not
specified, this command upgrades to the most recent version.
This option can only be used to increase the version number,
and only up to the most recent version supported by this
software.
-a Upgrade all file systems on all imported pools.
filesystem
Upgrade the specified file system.
zfsuserspace [-Hinp] [-ofield[,field]...] [-sfield]... [-Sfield]...
[-ttype[,type]...] filesystem|snapshot
Displays space consumed by, and quotas on, each user in the specified
filesystem or snapshot. This corresponds to the userused@user and
userquota@user properties.
-n Print numeric ID instead of user/group name.
-H Do not print headers, use tab-delimited output.
-p Use exact (parsable) numeric output.
-ofield[,field]...
Display only the specified fields from the following set:
type,name,used,quota. The default is to display all fields.
-sfield
Sort output by this field. The -s and -S flags may be speci-
fied multiple times to sort first by one field, then by
another. The default is -stype-sname.
-Sfield
Sort by this field in reverse order. See -s.
-ttype[,type]...
Print only the specified types from the following set:
all,posixuser,smbuser,posixgroup,smbgroup.
The default is -tposixuser,smbuser.
The default can be changed to include group types.
-i Translate SID to POSIX ID. This flag currently has no effect
on FreeBSD.
zfsgroupspace [-Hinp] [-ofield[,field]...] [-sfield]... [-Sfield]...
[-ttype[,type]...] filesystem|snapshot
Displays space consumed by, and quotas on, each group in the speci-
fied filesystem or snapshot. This subcommand is identical to "zfsuserspace", except that the default types to display are -tposixgroup,smbgroup.
zfsmount
Displays all ZFS file systems currently mounted.
-fzfsmount [-vO] [-oproperty[,property]...] -a | filesystem
Mounts ZFS file systems.
-v Report mount progress.
-O Perform an overlay mount. Overlay mounts are not supported on
FreeBSD.
-oproperty[,property]...
An optional, comma-separated list of mount options to use
temporarily for the duration of the mount. See the "TemporaryMountPointProperties" section for details.
-a Mount all available ZFS file systems. This command may be
executed on FreeBSD system startup by /etc/rc.d/zfs. For
more information, see variable zfs_enable in rc.conf(5).
filesystem
Mount the specified filesystem.
zfsunmount|umount [-f] -a | filesystem|mountpoint
Unmounts currently mounted ZFS file systems.
-f Forcefully unmount the file system, even if it is currently
in use.
-a Unmount all available ZFS file systems.
filesystem | mountpoint
Unmount the specified filesystem. The command can also be
given a path to a ZFS file system mount point on the system.
zfsshare-a | filesystem
Shares ZFS file systems that have the sharenfs property set.
-a Share all ZFS file systems that have the sharenfs property
set. This command may be executed on FreeBSD system startup
by /etc/rc.d/zfs. For more information, see variable
zfs_enable in rc.conf(5).
filesystem
Share the specified filesystem according to the sharenfs
property. File systems are shared when the sharenfs property
is set.
zfsunshare-a | filesystem|mountpoint
Unshares ZFS file systems that have the sharenfs property set.
-a Unshares ZFS file systems that have the sharenfs property
set. This command may be executed on FreeBSD system shutdown
by /etc/rc.d/zfs. For more information, see variable
zfs_enable in rc.conf(5).
filesystem | mountpoint
Unshare the specified filesystem. The command can also be
given a path to a ZFS file system shared on the system.
zfsbookmarksnapshotbookmark
Creates a bookmark of the given snapshot. Bookmarks mark the point
in time when the snapshot was created, and can be used as the incre-
mental source for a "zfssend" command.
This feature must be enabled to be used. See zpool-features(7) for
details on ZFS feature flags and the bookmark feature.
zfssend [-DnPpRve] [-isnapshot | -Isnapshot] snapshot
Creates a stream representation of the last snapshot argument (not
part of -i or -I) which is written to standard output. The output can
be redirected to a file or to a different system (for example, using
ssh(1)). By default, a full stream is generated.
-isnapshot
Generate an incremental stream from the first snapshot (the
incremental source) to the second snapshot (the incremental
target). The incremental source can be specified as the last
component of the snapshot name (the @ character and
following) and it is assumed to be from the same file system
as the incremental target.
If the destination is a clone, the source may be the origin
snapshot, which must be fully specified (for example,
pool/fs@origin, not just @origin).
-Isnapshot
Generate a stream package that sends all intermediary snap-
shots from the first snapshot to the second snapshot. For
example, -I@afs@d is similar to -i@afs@b;-i@bfs@c;-i@cfs@d. The incremental source may be specified as with the
-i option.
-R Generate a replication stream package, which will replicate
the specified filesystem, and all descendent file systems, up
to the named snapshot. When received, all properties, snap-
shots, descendent file systems, and clones are preserved.
If the -i or -I flags are used in conjunction with the -R
flag, an incremental replication stream is generated. The
current values of properties, and current snapshot and file
system names are set when the stream is received. If the -F
flag is specified when this stream is received, snapshots and
file systems that do not exist on the sending side are
destroyed.
-D Generate a deduplicated stream. Blocks which would have been
sent multiple times in the send stream will only be sent
once. The receiving system must also support this feature to
receive a deduplicated stream. This flag can be used regard-
less of the dataset's dedup property, but performance will be
much better if the filesystem uses a dedup-capable checksum
(eg. sha256).
-e Generate a more compact stream by using WRITE_EMBEDDED
records for blocks which are stored more compactly on disk by
the embedded_data pool feature. This flag has no effect if
the embedded_data feature is disabled. The receiving system
must have the embedded_data feature enabled. If the
lz4_compress feature is active on the sending system, then
the receiving system must have that feature enabled as well.
See zpool-features(7) for details on ZFS feature flags and
the embedded_data feature.
-p Include the dataset's properties in the stream. This flag is
implicit when -R is specified. The receiving system must also
support this feature.
-n Do a dry-run ("No-op") send. Do not generate any actual send
data. This is useful in conjunction with the -v or -P flags
to determine what data will be sent.
-P Print machine-parsable verbose information about the stream
package generated.
-v Print verbose information about the stream package generated.
This information includes a per-second report of how much
data has been sent.
The format of the stream is committed. You will be able to receive
your streams on future versions of ZFS.
zfssend [-e] [-isnapshot|bookmark] filesystem|volume|snapshot
Generate a send stream, which may be of a filesystem, and may be
incremental from a bookmark. If the destination is a filesystem or
volume, the pool must be read-only, or the filesystem must not be
mounted. When the stream generated from a filesystem or volume is
received, the default snapshot name will be (--head--).
-isnapshot|bookmark
Generate an incremental send stream. The incremental source
must be an earlier snapshot in the destination's history. It
will commonly be an earlier snapshot in the destination's
filesystem, in which case it can be specified as the last
component of the name (the # or @ character and following).
If the incremental target is a clone, the incremental source
can be the origin snapshot, or an earlier snapshot in the
origin's filesystem, or the origin's origin, etc.
-e Generate a more compact stream by using WRITE_EMBEDDED
records for blocks which are stored more compactly on disk by
the embedded_data pool feature. This flag has no effect if
the embedded_data feature is disabled. The receiving system
must have the embedded_data feature enabled. If the
lz4_compress feature is active on the sending system, then
the receiving system must have that feature enabled as well.
See zpool-features(7) for details on ZFS feature flags and
the embedded_data feature.
zfsreceive|recv [-vnFu] filesystem|volume|snapshotzfsreceive|recv [-vnFu] [-d | -e] filesystem
Creates a snapshot whose contents are as specified in the stream pro-
vided on standard input. If a full stream is received, then a new
file system is created as well. Streams are created using the "zfssend" subcommand, which by default creates a full stream. "zfsrecv"
can be used as an alias for "zfsreceive".
If an incremental stream is received, then the destination file sys-
tem must already exist, and its most recent snapshot must match the
incremental stream's source. For zvols, the destination device link
is destroyed and recreated, which means the zvol cannot be accessed
during the receive operation.
When a snapshot replication package stream that is generated by using
the "zfssend-R" command is received, any snapshots that do not
exist on the sending location are destroyed by using the "zfsdestroy-d" command.
The name of the snapshot (and file system, if a full stream is
received) that this subcommand creates depends on the argument type
and the -d or -e option.
If the argument is a snapshot name, the specified snapshot is cre-
ated. If the argument is a file system or volume name, a snapshot
with the same name as the sent snapshot is created within the speci-
fied filesystem or volume. If the -d or -e option is specified, the
snapshot name is determined by appending the sent snapshot's name to
the specified filesystem. If the -d option is specified, all but the
pool name of the sent snapshot path is appended (for example, b/c@1
appended from sent snapshot a/b/c@1), and if the -e option is speci-
fied, only the tail of the sent snapshot path is appended (for exam-
ple, c@1 appended from sent snapshot a/b/c@1). In the case of -d,
any file systems needed to replicate the path of the sent snapshot
are created within the specified file system.
-d Use the full sent snapshot path without the first element
(without pool name) to determine the name of the new snapshot
as described in the paragraph above.
-e Use only the last element of the sent snapshot path to deter-
mine the name of the new snapshot as described in the para-
graph above.
-u File system that is associated with the received stream is
not mounted.
-v Print verbose information about the stream and the time
required to perform the receive operation.
-n Do not actually receive the stream. This can be useful in
conjunction with the -v option to verify the name the receive
operation would use.
-F Force a rollback of the file system to the most recent snap-
shot before performing the receive operation. If receiving an
incremental replication stream (for example, one generated by
"zfssend-R-Fi-iI"), destroy snapshots and file systems
that do not exist on the sending side.
zfsallowfilesystem|volume
Displays permissions that have been delegated on the specified
filesystem or volume. See the other forms of "zfsallow" for more
information.
zfsallow [-ldug] user|group[,user|group]...
perm|@setname[,perm|@setname]... filesystem|volumezfsallow [-ld] -e|everyoneperm|@setname[,perm|@setname]...
filesystem|volume
Delegates ZFS administration permission for the file systems to non-
privileged users.
[-ug] user|group[, user|group]...
Specifies to whom the permissions are delegated. Multiple
entities can be specified as a comma-separated list. If nei-
ther of the -ug options are specified, then the argument is
interpreted preferentially as the keyword everyone, then as a
user name, and lastly as a group name. To specify a user or
group named "everyone", use the -u or -g options. To specify
a group with the same name as a user, use the -g option.
[-e|everyone]
Specifies that the permissions be delegated to "everyone".
perm|@setname[,perm|@setname]...
The permissions to delegate. Multiple permissions may be
specified as a comma-separated list. Permission names are the
same as ZFS subcommand and property names. See the property
list below. Property set names, which begin with an at sign
(@), may be specified. See the -s form below for details.
[-ld] filesystem|volume
Specifies where the permissions are delegated. If neither of
the -ld options are specified, or both are, then the permis-
sions are allowed for the file system or volume, and all of
its descendents. If only the -l option is used, then is
allowed "locally" only for the specified file system. If
only the -d option is used, then is allowed only for the
descendent file systems.
Permissions are generally the ability to use a ZFS subcommand or
change a ZFS property. The following permissions are available:
NAME TYPE NOTES
allow subcommand Must also have the permission
that is being allowed
clone subcommand Must also have the 'create'
ability and 'mount' ability in
the origin file system
create subcommand Must also have the 'mount'
ability
destroy subcommand Must also have the 'mount'
ability
diff subcommand Allows lookup of paths within a
dataset given an object number,
and the ability to create snap-
shots necessary to 'zfs diff'
hold subcommand Allows adding a user hold to a
snapshot
mount subcommand Allows mount/umount of ZFS
datasets
promote subcommand Must also have the 'mount' and
'promote' ability in the origin
file system
receive subcommand Must also have the 'mount' and
'create' ability
release subcommand Allows releasing a user hold
which might destroy the snapshot
rename subcommand Must also have the 'mount' and
'create' ability in the new
parent
rollback subcommand Must also have the 'mount'
ability
send subcommand
share subcommand Allows sharing file systems over
the NFS protocol
snapshot subcommand Must also have the 'mount'
ability
groupquota other Allows accessing any
groupquota@... property
groupused other Allows reading any groupused@...
property
userprop other Allows changing any user property
userquota other Allows accessing any
userquota@... property
userused other Allows reading any userused@...
property
aclinherit property
aclmode property
atime property
canmount property
casesensitivity property
checksum property
compression property
copies property
dedup property
devices property
exec property
filesystem_limit property
logbias property
jailed property
mlslabel property
mountpoint property
nbmand property
normalization property
primarycache property
quota property
readonly property
recordsize property
refquota property
refreservation property
reservation property
secondarycache property
setuid property
sharenfs property
sharesmb property
snapdir property
snapshot_limit property
sync property
utf8only property
version property
volblocksize property
volsize property
vscan property
xattr property
zfsallow-cperm|@setname[,perm|@setname]... filesystem|volume
Sets "create time" permissions. These permissions are granted
(locally) to the creator of any newly-created descendent file system.
zfsallow-s@setnameperm|@setname[,perm|@setname]... filesystem|volume
Defines or adds permissions to a permission set. The set can be used
by other "zfsallow" commands for the specified file system and its
descendents. Sets are evaluated dynamically, so changes to a set are
immediately reflected. Permission sets follow the same naming
restrictions as ZFS file systems, but the name must begin with an "at
sign" (@), and can be no more than 64 characters long.
zfsunallow [-rldug] user|group[,user|group]...
[perm|@setname[,perm|@setname]...] filesystem|volumezfsunallow [-rld] -e|everyone [perm|@setname[,perm|@setname]...]
filesystem|volumezfsunallow [-r] -c [perm|@setname[,perm|@setname]...] filesystem|volume
Removes permissions that were granted with the "zfsallow" command.
No permissions are explicitly denied, so other permissions granted
are still in effect. For example, if the permission is granted by an
ancestor. If no permissions are specified, then all permissions for
the specified user, group, or everyone are removed. Specifying
everyone (or using the -e option) only removes the permissions that
were granted to everyone, not all permissions for every user and
group. See the "zfsallow" command for a description of the -ldugec
options.
-r Recursively remove the permissions from this file system and
all descendents.
zfsunallow [-r] -s@setname [perm|@setname[,perm|@setname]...]
filesystem|volume
Removes permissions from a permission set. If no permissions are
specified, then all permissions are removed, thus removing the set
entirely.
zfshold [-r] tagsnapshot...
Adds a single reference, named with the tag argument, to the speci-
fied snapshot or snapshots. Each snapshot has its own tag namespace,
and tags must be unique within that space.
If a hold exists on a snapshot, attempts to destroy that snapshot by
using the "zfsdestroy" command returns EBUSY.
-r Specifies that a hold with the given tag is applied recur-
sively to the snapshots of all descendent file systems.
zfsholds [-r] snapshot...
Lists all existing user references for the given snapshot or snap-
shots.
-r Lists the holds that are set on the named descendent snap-
shots, in addition to listing the holds on the named snap-
shot.
zfsrelease [-r] tagsnapshot...
Removes a single reference, named with the tag argument, from the
specified snapshot or snapshots. The tag must already exist for each
snapshot.
-r Recursively releases a hold with the given tag on the snap-
shots of all descendent file systems.
zfsdiff [-FHt] snapshot [snapshot|filesystem]
Display the difference between a snapshot of a given filesystem and
another snapshot of that filesystem from a later time or the current
contents of the filesystem. The first column is a character indicat-
ing the type of change, the other columns indicate pathname, new
pathname (in case of rename), change in link count, and optionally
file type and/or change time.
The types of change are:
- path was removed
+ path was added
M path was modified
R path was renamed
-F Display an indication of the type of file, in a manner simi-
lar to the -F option of ls(1).
B block device
C character device
F regular file
/ directory
@ symbolic link
= socket
> door (not supported on FreeBSD)
| named pipe (not supported on FreeBSD)
P event port (not supported on FreeBSD)
-H Give more parsable tab-separated output, without header lines
and without arrows.
-t Display the path's inode change time as the first column of
output.
zfsjailjailidfilesystem
Attaches the specified filesystem to the jail identified by JID
jailid. From now on this file system tree can be managed from within
a jail if the jailed property has been set. To use this functional-
ity, the jail needs the allow.mount and allow.mount.zfs parameters
set to 1 and the enforce_statfs parameter set to a value lower than
2.
See jail(8) for more information on managing jails and configuring
the parameters above.
zfsunjailjailidfilesystem
Detaches the specified filesystem from the jail identified by JID
jailid.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
1 An error occurred.
2 Invalid command line options were specified.
EXAMPLESExample1 Creating a ZFS File System Hierarchy
The following commands create a file system named pool/home and a file
system named pool/home/bob. The mount point /home is set for the par-
ent file system, and is automatically inherited by the child file sys-
tem.
# zfscreatepool/home
# zfssetmountpoint=/homepool/home
# zfscreatepool/home/bobExample2 Creating a ZFS Snapshot
The following command creates a snapshot named yesterday. This snap-
shot is mounted on demand in the .zfs/snapshot directory at the root of
the pool/home/bob file system.
# zfssnapshotpool/home/bob@yesterdayExample3 Creating and Destroying Multiple Snapshots
The following command creates snapshots named yesterday of pool/home
and all of its descendent file systems. Each snapshot is mounted on
demand in the .zfs/snapshot directory at the root of its file system.
The second command destroys the newly created snapshots.
# zfssnapshot-rpool/home@yesterday
# zfsdestroy-rpool/home@yesterdayExample4 Disabling and Enabling File System Compression
The following command disables the compression property for all file
systems under pool/home. The next command explicitly enables
compression for pool/home/anne.
# zfssetcompression=offpool/home
# zfssetcompression=onpool/home/anneExample5 Listing ZFS Datasets
The following command lists all active file systems and volumes in the
system. Snapshots are displayed if the listsnaps property is on. The
default is off. See zpool(8) for more information on pool properties.
# zfslist
NAME USED AVAIL REFER MOUNTPOINT
pool 450K 457G 18K /pool
pool/home 315K 457G 21K /home
pool/home/anne 18K 457G 18K /home/anne
pool/home/bob 276K 457G 276K /home/bob
Example6 Setting a Quota on a ZFS File System
The following command sets a quota of 50 Gbytes for pool/home/bob.
# zfssetquota=50Gpool/home/bobExample7 Listing ZFS Properties
The following command lists all properties for pool/home/bob.
# zfsgetallpool/home/bob
NAME PROPERTY VALUE SOURCE
pool/home/bob type filesystem -
pool/home/bob creation Tue Jul 21 15:53 2009 -
pool/home/bob used 21K -
pool/home/bob available 20.0G -
pool/home/bob referenced 21K -
pool/home/bob compressratio 1.00x -
pool/home/bob mounted yes -
pool/home/bob quota 20G local
pool/home/bob reservation none default
pool/home/bob recordsize 128K default
pool/home/bob mountpoint /home/bob default
pool/home/bob sharenfs off default
pool/home/bob checksum on default
pool/home/bob compression on local
pool/home/bob atime on default
pool/home/bob devices on default
pool/home/bob exec on default
pool/home/bob filesystem_limit none default
pool/home/bob setuid on default
pool/home/bob readonly off default
pool/home/bob jailed off default
pool/home/bob snapdir hidden default
pool/home/bob snapshot_limit none default
pool/home/bob aclmode discard default
pool/home/bob aclinherit restricted default
pool/home/bob canmount on default
pool/home/bob xattr on default
pool/home/bob copies 1 default
pool/home/bob version 5 -
pool/home/bob utf8only off -
pool/home/bob normalization none -
pool/home/bob casesensitivity sensitive -
pool/home/bob vscan off default
pool/home/bob nbmand off default
pool/home/bob sharesmb off default
pool/home/bob refquota none default
pool/home/bob refreservation none default
pool/home/bob primarycache all default
pool/home/bob secondarycache all default
pool/home/bob usedbysnapshots 0 -
pool/home/bob usedbydataset 21K -
pool/home/bob usedbychildren 0 -
pool/home/bob usedbyrefreservation 0 -
pool/home/bob logbias latency default
pool/home/bob dedup off default
pool/home/bob mlslabel -
pool/home/bob sync standard default
pool/home/bob refcompressratio 1.00x -
The following command gets a single property value.
# zfsget-H-ovaluecompressionpool/home/bob
on
The following command lists all properties with local settings for
pool/home/bob.
# zfsget-slocal-oname,property,valueallpool/home/bob
NAME PROPERTY VALUE
pool/home/bob quota 20G
pool/home/bob compression on
Example8 Rolling Back a ZFS File System
The following command reverts the contents of pool/home/anne to the
snapshot named yesterday, deleting all intermediate snapshots.
# zfsrollback-rpool/home/anne@yesterdayExample9 Creating a ZFS Clone
The following command creates a writable file system whose initial con-
tents are the same as pool/home/bob@yesterday.
# zfsclonepool/home/bob@yesterdaypool/cloneExample10 Promoting a ZFS Clone
The following commands illustrate how to test out changes to a file
system, and then replace the original file system with the changed one,
using clones, clone promotion, and renaming:
# zfscreatepool/project/production
Populate /pool/project/production with data and continue with the fol-
lowing commands:
# zfssnapshotpool/project/production@today
# zfsclonepool/project/production@todaypool/project/beta
Now make changes to /pool/project/beta and continue with the following
commands:
# zfspromotepool/project/beta
# zfsrenamepool/project/productionpool/project/legacy
# zfsrenamepool/project/betapool/project/production
Once the legacy version is no longer needed, it can be destroyed.
# zfsdestroypool/project/legacyExample11 Inheriting ZFS Properties
The following command causes pool/home/bob and pool/home/anne to
inherit the checksum property from their parent.
# zfsinheritchecksumpool/home/bobpool/home/anneExample12 Remotely Replicating ZFS Data
The following commands send a full stream and then an incremental
stream to a remote machine, restoring them into poolB/received/fs@a and
poolB/received/fs@b, respectively. poolB must contain the file system
poolB/received, and must not initially contain poolB/received/fs.
# zfssendpool/fs@a | sshhostzfsreceivepoolB/received/fs@a
# zfssend-iapool/fs@b | sshhostzfsreceivepoolB/received/fsExample13 Using the "zfs receive -d" Option
The following command sends a full stream of poolA/fsA/fsB@snap to a
remote machine, receiving it into poolB/received/fsA/fsB@snap. The
fsA/fsB@snap portion of the received snapshot's name is determined from
the name of the sent snapshot. poolB must contain the file system
poolB/received. If poolB/received/fsA does not exist, it is created as
an empty file system.
# zfssendpoolA/fsA/fsB@snap | sshhostzfsreceive-dpoolB/receivedExample14 Setting User Properties
The following example sets the user-defined com.example:department
property for a dataset.
# zfssetcom.example:department=12345tank/accountingExample15 Performing a Rolling Snapshot
The following example shows how to maintain a history of snapshots with
a consistent naming scheme. To keep a week's worth of snapshots, the
user destroys the oldest snapshot, renames the remaining snapshots, and
then creates a new snapshot, as follows:
# zfsdestroy-rpool/users@7daysago
# zfsrename-rpool/users@6daysago@7daysago
# zfsrename-rpool/users@5daysago@6daysago
# zfsrename-rpool/users@4daysago@5daysago
# zfsrename-rpool/users@3daysago@4daysago
# zfsrename-rpool/users@2daysago@3daysago
# zfsrename-rpool/users@yesterday@2daysago
# zfsrename-rpool/users@today@yesterday
# zfssnapshot-rpool/users@todayExample16 Setting "sharenfs" Property Options on a ZFS File System
The following command shows how to set sharenfs property options to
enable root access for a specific network on the tank/home file system.
The contents of the sharenfs property are valid exports(5) options.
# zfssetsharenfs="maproot=root,network192.168.0.0/24"tank/home
Another way to write this command with the same result is:
# setzfssharenfs="-maproot=root-network192.168.0.0/24"tank/homeExample17 Delegating ZFS Administration Permissions on a ZFS Dataset
The following example shows how to set permissions so that user cindys
can create, destroy, mount, and take snapshots on tank/cindys. The
permissions on tank/cindys are also displayed.
# zfsallowcindyscreate,destroy,mount,snapshottank/cindys
# zfsallowtank/cindys
-------------------------------------------------------------
Local+Descendent permissions on (tank/cindys)
user cindys create,destroy,mount,snapshot
-------------------------------------------------------------
Example18 Delegating Create Time Permissions on a ZFS Dataset
The following example shows how to grant anyone in the group staff to
create file systems in tank/users. This syntax also allows staff mem-
bers to destroy their own file systems, but not destroy anyone else's
file system. The permissions on tank/users are also displayed.
# zfsallowstaffcreate,mounttank/users
# zfsallow-cdestroytank/users
# zfsallowtank/users
-------------------------------------------------------------
Create time permissions on (tank/users)
create,destroy
Local+Descendent permissions on (tank/users)
group staff create,mount
-------------------------------------------------------------
Example19 Defining and Granting a Permission Set on a ZFS Dataset
The following example shows how to define and grant a permission set on
the tank/users file system. The permissions on tank/users are also dis-
played.
# zfsallow-s@psetcreate,destroy,snapshot,mounttank/users
# zfsallowstaff@psettank/users
# zfsallowtank/users
-------------------------------------------------------------
Permission sets on (tank/users)
@pset create,destroy,mount,snapshot
Create time permissions on (tank/users)
create,destroy
Local+Descendent permissions on (tank/users)
group staff @pset,create,mount
-------------------------------------------------------------
Example20 Delegating Property Permissions on a ZFS Dataset
The following example shows to grant the ability to set quotas and
reservations on the users/home file system. The permissions on
users/home are also displayed.
# zfsallowcindysquota,reservationusers/home
# zfsallowcindys
-------------------------------------------------------------
Local+Descendent permissions on (users/home)
user cindys quota,reservation
-------------------------------------------------------------
# su-cindys
cindys% zfssetquota=10Gusers/home/marks
cindys% zfsgetquotausers/home/marks
NAME PROPERTY VALUE SOURCE
users/home/marks quota 10G local
Example21 Removing ZFS Delegated Permissions on a ZFS Dataset
The following example shows how to remove the snapshot permission from
the staff group on the tank/users file system. The permissions on
tank/users are also displayed.
# zfsunallowstaffsnapshottank/users
# zfsallowtank/users
-------------------------------------------------------------
Permission sets on (tank/users)
@pset create,destroy,mount,snapshot
Create time permissions on (tank/users)
create,destroy
Local+Descendent permissions on (tank/users)
group staff @pset,create,mount
-------------------------------------------------------------
Example22ShowingthedifferencesbetweenasnapshotandaZFSDataset
The following example shows how to see what has changed between a prior
snapshot of a ZFS Dataset and its current state. The -F option is used
to indicate type information for the files affected.
# zfsdifftank/test@beforetank/test
M / /tank/test/
M F /tank/test/linked (+1)
R F /tank/test/oldname -> /tank/test/newname
- F /tank/test/deleted
+ F /tank/test/created
M F /tank/test/modified
SEE ALSOchmod(2), fsync(2), exports(5), fstab(5), rc.conf(5), jail(8), mount(8),
umount(8), zpool(8)AUTHORS
This manual page is a mdoc(7) reimplementation of the OpenSolaris manual
page zfs(1M), modified and customized for FreeBSD and licensed under the
Common Development and Distribution License (CDDL).
The mdoc(7) implementation of this manual page was initially written by
Martin Matuska <mm@FreeBSD.org>.
FreeBSD 10.1 June 30, 2014 FreeBSD 10.1